negative scores for internal mail

[Nate Kroll <kr...@msoe.edu>]

Recently we have had some computers on our network become infected with
viruses that send emails to random users on our exchange server and our
list server.  While we can't stop the emails going to the exchange server,
we can filter the ones going to the list server because it is on our main
mail exchanger (where SA resides).  However, the spam emails being sent to
the lists addresses are being filtered but having very low negative
scores, like in the -17 to -30 range.  I've turned off bayesian filtering
and auto learn to make sure they don't play a role.  I'm just wondering if
there is something in spamassassin or amavis that sets a score lower since
it's from inside our own domain or if there is another way to have the
emails have normal scores?

We have spamassassin involed by amavis from postfix on our debian unstable
mail server.  We are running spamassassin version 3.0.3 on perl 5.8.4.

Any help or ideas are greatly appreciated.  Thanks!

Nate Kroll
MSOE